I'm just starting to look at this family too.
I have an Amos Cook b. c. 1773 or 1774 in the Huntington (AKA Norwich) area of Hampshire Co., MA and there is a Mace Cook living there as early as 1773 (he's in tax records there in 1773 and 1774). I've also seen Mace spelled Masa in several family trees.
When Amos Cook married for the first time (I'm descended from his second marriage), there is an entry just below his that Widow Silence Cook married a George Manley of Sandsfield MA in Aug 1798. Mace supposedly died in 1797 in Norwich. I'm wondering if Amos was Mace/Masa and Silence's son.
Mace was also listed as a town tythingman in Norwich in 1780-81.